There's a big advantage to using multiple packs in parralel or series config and that is if one set of cells dies, then you can get rid of that pack and buy a new one for half or less of the cost. The 2200 mah 3S packs now are getting down right cheap. Hobbycity is doing a good job of getting bigger packs and many different configurations. Jose and I agree on one thing though, 4S is too small for your app and the size of plane you want, like he said, it would be more suitable for a .25-.32 size plane.
Good luck and ask questions,
Curtis